1. Field of the Invention
The present invention relates to an endoscope apparatus comprising a curved-shape detection sensor that detects a curved shape of a distal insertion tube of an endoscope.
2. Description of the Related Art
An endoscope comprising an elongated distal insertion tube to be inserted in an insertion target, the distal insertion tube being provided with a curved-shape detection sensor to detect a curved shape (a curved angle and a curved direction) of the distal insertion tube has been known. Such a curved-shape detection sensor is provided with a sensing part for detecting a curved shape. The curved-shape detection sensor detects the amount of change of detection light at the sensing part by a light detector, thereby detecting the curved shape of the distal insertion tube.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2007-44402 discloses an endoscope apparatus comprising a light guide, curvature detection fibers, a filter, and a light receiving element. In the endoscope apparatus, a plurality of curvature detection fibers are arranged on the outer peripheral surface of a light guide in an insertion tube of an endoscope. The light guide and the curvature detection fibers extend along the insertion tube to the distal end. The filter covers an output end of the light guide and an input end of each curvature detecting fiber. A sensing part is provided in each curvature detection fiber in a predetermined position and a predetermined orientation.
In the endoscope apparatus, light output from a light source to the input end of the light guide is guided from the output end of the light guide through the filter to the input end of each curvature detection fiber. Part of the light input from the input end is lost when passing the sensing part. The endoscope apparatus detects a curved shape of the insertion tube in the sensing part based on the amount of light received at the light receiving element from the output end of each curvature detection fiber. The light guide also plays a role of transmitting illumination light to an illumination optical system at the distal end of the insertion tube.